Add request permissions tool (#13092)

Adds a built-in `request_permissions` tool and wires it through the
Codex core, protocol, and app-server layers so a running turn can ask
the client for additional permissions instead of relying on a static
session policy.

The new flow emits a `RequestPermissions` event from core, tracks the
pending request by call ID, forwards it through app-server v2 as an
`item/permissions/requestApproval` request, and resumes the tool call
once the client returns an approved subset of the requested permission
profile.

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -695,6 +695,12 @@ server_request_definitions! {
         response: v2::McpServerElicitationRequestResponse,
     },
 
+    /// Request approval for additional permissions from the user.
+    PermissionsRequestApproval => "item/permissions/requestApproval" {
+        params: v2::PermissionsRequestApprovalParams,
+        response: v2::PermissionsRequestApprovalResponse,
+    },
+
     /// Execute a dynamic tool call on the client.
     DynamicToolCall => "item/tool/call" {
         params: v2::DynamicToolCallParams,